Over the last decade, the amount of wireless traffic has greatly increased, and devices such as smartphones and tablets have become ubiquitous. Due to the enhanced connectivity and the wide use of applications that require data transmission these devices and their applications may use significantly more spectrum than feature phones or standard mobile devices. Several studies predict tremendous worldwide growth in the market size of mobile broadband services. For instance, according to one study, the market may grow from 1 billion users as estimated in 2012 to as many as 8 billion users by 2015. In addition, global mobile data continues to double yearly and may continue to do so through 2016. Thus, more spectrum may be needed for mobile broadband use.
Traditionally, spectrum use has been based on exclusive utilization of dedicated bands, and additional spectrum for mobile broadband has been created by repurposing of spectrum (i.e. moving incumbents to other bands). This happened for example with the 2.5 GHz band in most parts of the world, and more recently with the clearing of parts of the UHF band due to the digital switchover, known as the Digital Dividend. With time, the practice of repurposing has become more difficult due to the nature of the incumbent services that would need to be moved to other bands. In particular, repurposing of existing services that are widely in use is an extremely costly and lengthy undertaking. As a result, regulators have begun to realize that methods other than repurposing may be used to obtain new spectrum to solve the bandwidth crunch. For example, most of the spectrum bands are not fully utilized, and portions of them may be available for other uses on a geographical or temporal basis.